Conductive fluid electrical contact device



R. E. PARIS Feb. 1o, 194s.

AkCONDUCTIVE FLUIDELECTRICAL CONTACT DEVICE Filed Oct. 9, 1945 5 Sheets-Sheet l N .UNR

A TTORN'X Feb.l 10, 1948. R. E. PARIS 2,435,725

CQNDUCTIVE FLUID ELECTRICAL CONTACT DEVICE Filed Oct. 9, 1943 3 Sheets-Sheet 2 /fd #5 #4 -FIG3. I *Vf nnunnn n nnnnn ununnn nnunnn UDDUUD INVENTOR. f @05E/Q7 E. PAQ/s.

ATToR/vy Patented Feb. 10, r`1948 CONDUCTIVE FLUID ELECTRICAL CONTACT DEVICE Robert E. Paris, Teaneck, N. J., assigner to International Business Machines Corporation, New York, N. Y., a corporation of New York Application October 9, 1943, Serial No. 505,687

8 Claims.

This invention relates to electrical sensing devices, its principal object being to provide an eicient and reliable means for sensing sheets of insulating material, or portions thereof, in order to detect an edge of the sheet, or a perforation therein.

In accordance with the principle of the invention an electrically conductive uid is used as the effective sensing instrumentality. The conductive iiuid is positioned by suitable supporting -means so as to make contact with one surface of the sheet and is complemented by a counter contact device positioned to make contact with said conductive uid, subject to the interposition of the insulating sheet between the complementary contact areas of the counter contact and the conductive iiuid.

One advantage of the use of a conductive fluid as the effective sensing instrumentality, particularly where the insulating sheet is sensed in motion, is that the fluid iiows instantly, on being released by the arrival of a, perforation, or edge of the sheet, at the Contact area, and makes and maintains continuous contact with the counter contact, until separated by the sheet again. The iluid nature of the sensing instrumentality enables it to sense very small perforations in a moving sheet. This operation can be enhanced, in accordance with a particular feature of the invention, by maintaining the conductive fluid under a yielding hydrostatic pressure during the sensing.

Accordingly, one advantage of the invention, as applied to the reading of control records, is that it increases the speed and reliability of the sensing operation.

Another advantage is that it will read smaller perforations than those now commonly used in perforated records.

Another advantage is that it is capable of sensing extremely small perforatlons in moving records.

Another advantage is that it allows a greater tolerancey of variations in the position of the perforations, while providing exact limits of tolerance. l

Another advantage is that it produces no dust from the records, such as brush sensing mechanisms are known to produce. Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 is a partly diagrammatic vertical sectional view showing a, tabulating machine embodying a sensing mechanism in accordance with the invention, the section through the sensing mechanism being on the line l-l of Fig. 3.

Fig. 2 is a detail side elevation of a part of the driving mechanism.

Fig. 3 is a vertical section through the sensing mechanism, parallel to the shafts of the sensing rollers.

Fig. 4 is a vertical section at .right angles to Fig. 3, on the line 4 4.

Fig. 5 is a detail view of a portion of the gearing which drives the sensing rollers and the feed rollers.

Figs. 6, 7, and 8 are detail sectional views on a large scale of portions of three modifications of the sensing mechanism.

Fig. 9 is a portion of a record card.

Fig. 10 is a senil-diagrammatic vertical sectional view of a modified tabulating machine,

yin which the invention is applied to the function of detecting the presence of a control record at the sensing rollers, in place of the card lever used for this purpose in Fig. 1.

Fig. 11 is a detail view on an enlarged scale of portions of the sensing rollers shown in Fig. 10.

Fig. 12 is a detail view, partly in section, of the sensing rollers disclosed in Fig. 10, showing portions of the latter in side elevation.

Background structure of the illustrative embodiment The machine partially shown in Fig. 1 is a ta'oulating machine designed `to feed record cards in sequence through a reading mechanism R, which analyzes the cards and controls a printing mechanism P, whereby the data from the record cards is tabulated in printed form. Such a machine ordinarily includes accumulators for totalizing statistical data, but these are not shown in the drawing since the printing mechanism will sufficiently illustrate the manner in which the record reading mechanism controls another mechanism. The printing mechanism would ordinarily be positioned beside the card feeding mechanism, but has been moved to the right in Fig. 1, to make it visible in the same view.

The Driving Mechanism The drive of the machine is taken from an electric motor M, the shaft of which is connected by a belt I0 to a pulley Il on a shaft I2. This Shaft has fixed to it a, notched disk, I3 and revolubly mounted on it a unit comprising an arm I4 connected by a hub I5 (Fig. 2) to a gear I6. The arm I4 has pivoted to it a dog I1 adapted to engage the notch of the dirk I3. When the machine is not feeding cards, the arm I4 is latched by a latch I8 which also engages the firger Ila of the dog I1 and retracts the dog from the notch, against the pull of a spring I9. The latch I8 is pivoted at 20 on a magnet frame 2I and normally pulled clockwise by a spring 22. A detent 23 pivoted to the latch I8 Vand biased by a spring (not shown) engages behind the arm I4 when the latter islstopped by the latch and locks the unit comprising thearm I4 and gear I6 in a fixed position. The latch I8 can be released from the arm I4 by a magnet e CFM. When the latch I8 releasesthe arm I4 and nger Ila, the dog I1 drops onto the disk I3 and engages the notch thereof, setting the arm I4 and gear I6 in rotation. The rotation will continue as long as the magnet CFM remains energized.

The Card Feeding Mechanism The card feeding mechanism is of a well known type shown in Carroll Patent 1,791,883. The cards C are stacked in a hopper 25 and fed singly from the bottom of the stack by a reciprocating picker 26 operated by a lever 21. The lever is driven by a link 28 connected to an eccentric pin 29 on gear I6. The picker feeds a card for each revolution of the gear I6. The cards, on emerging from the hopper, are engaged by a rst pair of feed rollers 30 and 3l, by which they are fed to a second pair of feed rollers 32 and 33. The latter feed the cards to the sensing mechanism, which comprises a lower roller 34 and an upper roller 35, the construction of which will be described in detail presently. The cards are received from the sensing rollers by a pair of feed rollers 36 and 31, which deposit them in a hopper 38. The feed rollers are journaled in frame plates 39a, and 39h (Fig. 3).

The drive of the sensing rollers and of all the feed rollers is taken from the gear I6 through a large gear 40, which meshes with a gear 4I on the near end (Fig. 1) of shaft 42 of the lower sensing roller 34 (see also Fig. 5). At the opposite end of shaft 42 is fixed a gear 43 meshing with a gear 44 fixed to the shaft 45 of the upper sensing roller 35. The lower feed rollers 30, 32 and 36 are geared to the sensing roller 34 by intermediate gears 46, 41, and 48 meshing, in the manner indicated by dot and dash lines in Fig. l, with gears U, 5I, 52, 53, which are respectively fixed to the shafts 42, 54, 55 and 56. The lower shafts 54, 55, 55 are geared to their respective upper shafts 51, 58, and 59 by pairs of gears 6I, 62; 63, 64; and 65, 66. The gearing is such as to impart the same peripheral speed to all of the rollers along the card feeding path. The gears I6 and 4I have the same number of teeth, hence the roller 34 makes one revolution for each revolution of the gear I6.

The printing mechanism.

The printing mechanism is of the kind shown in the Lake Patent 1,822,594 and comprises a set of type bars,.only one of which appears in the drawing at 18. These type bars are mounted so as to be movable up and down in relation to a platen 1I, on which a sheet of paper which is to receive the printed record is supported. A hammer 12 is pivotally mounted on a stationary bracket 13 so that its head is positioned in line with the printing line of the platen. There is a hammer for each type bar. The type bars can be raised to positions independently determined for each type bar, so that a selected one of the type members 14 is between the related printing hammer and the platen, at the end of the setting operation. For simplicity of illustration, the type mechanism shown has only the lten type members required for printing numerals.

A cross head 15, mounted for vertical movement on two bars, one of which is shown at '16, carries a bracket 11 having a cross rod 18 on which are mounted a number of arms 19, one for each type bar 1U. .'The arms 19 are biased upward by springs 8D to engage the bottom ends of their respective type bars. On one end of a rock shaft 8l is fixed an arm 82 carrying a link 33 pivotally connected to the adjacent end of the cross head 15. This mechanism is duplicated at the opposite end of the rock shaft 8l, which shaft also has fixed to it an arm 84 carrying a roller 85 traveling in a groove 86 of a cam 81 xedly mounted on a shaft 88. When the cam revolves, the cross head is raised and moves the type bars upward. The typebars arey differentially stopped in the course of their upward movement by individual dogs 98 pivoted on a stationary rod QI, each dog being biased in a clockwise direction by a spring 92 connected to an individual pivoted latch 93. The latch is connected by link 94 to an armature 95 of an electromagnet 56. When the electromagnet is energized, the latch releases the dog 90, which engages a particular tooth of a set of teeth 31 on the type bar. The upwardA movement of the type bars by the cam 81 is synchronized with the feed of the cards, so that as the index' point positions of the cards successively reach the sensing means, the teeth 91 of the type bars successively come into position to be stopped by the dog 90, if a perforation should' be sensed in the card. For this purpose the shaft 88- (indicated by dot and dash line 88a) is provided with a driving gear 99 having the same number of teeth as the gear I6 and meshing with the gear 40.

The illustrative machine shown in the drawing is designed to handle record cards similar to the well known Hollerith statistical cards, but different from those in use at present in one important respect, namely, inthe sizeof the hole used to represent the characters recorded. Fig. 9 shows a portion of such a modified Hollerith card. If this card be thought of asl having the usual length of 31/4 Vinches between the two long sides a and b, then the twelve index point positions 9-I, O, X, R have the usual spacing `of 1/4 inch. The small, round data-representing holes d, on the other hand, are only .04 of an inch in diameter, as compared with the customary size of (approximately) .125 by .O57 inches. A sensing mechanism constructed in accordance with my invention will reliably sense holes much smaller than .04 of an inch, with advantages apparent to those skilled in the art.

The sensing mechanism In accordance with the invention, the usual brush sensing means is replaced by two complementary sensing members, at least one of which has on its surface an electrically conductive fluid. The preferred electrically conductive fluid is mercury, or an amalgam having some fluidity. In the constructions shown'inthe drawing, the lower roller carries mercury on its surface, while the S upper roller has a`solid electrically conductive surface, preferably repellent to mercury.

Three illustrative constructions of the lower roller 34 are shown in Figs. 6, 7, and 8, respectively. In Fig. 6 the roller comprises a central metallic shaft d2 covered with an insulating sleeve IiIIl, the latter being covered with a metallic sleeve IlII, preferably of tin, silver, or a base metal plated with silver. Surrounding the sleeve IGI is a cylinder of rubber |62 with radial holes |63 partially lled by a metallic composition |64. The composition Iil should be one having a strong attraction for mercury, such as a silver amalgam composed of 50 parts mercury and 50 parts silver, and should make good electrical contact with the sleeve IIlI. The hoies in the rubber cylinder have the same spacing as the index points of the record cards and the roller is driven in timed relation to the feed of the cards from the hopper 25, so that the index point positions of the cards coincide with the successive holes.

The roller 36 is partially enclosed in a trough (Figs. 3 and 4) partly lled with mercury |06. As the roller turns in clockwise direction, the pockets |03 are submerged in the mercury and on emerging at the opposite side each is filled with a drop of mercury adhering to the amalgam in the pocket. A doctor blade lill reduces the mercury in all the pockets to about the level indicated at |63. The trough 05 is secured to the frame plates 39a and 3% by screws iti), and may be electrically insulated therefrom, as indicated. A scraper H5 may be provided to return to the trough |05 any stray droplets of mercury which might adhere to the card.

The upper roller 35 preferably comprises a central metallic shaft 45, an insulating sleeve Iii), a series of metal rings III, and an interspersed series of insulating rings II2. The metal rings I II are preferably composed of steel, which has no attraction for mercury. They are spaced by the insulating rings I I2 so as to have the same spacing as the pockets |63 on the lower roller, which conforms to the column spacing of the record cards. Each metal ring III has bearing upon it an individual brush II3, these brushes being secured upon an insulating bar IIA by means of individual terminal connectors I I5.

Sensing operation The sensing process is illustrated in Fig. 6. The upper and lower rollers are journaled so that they just make contact when no card is between them. When a card enters the bite of the rollers, the rubber surface of the lower roller yields to admit the card. As the rollers revolve, the drops of mercury in the cups I|l3 are successively laid upon the index point positions of the card and, as the pressure increases near the line of centers of the rollers, if there is a perforation in the card, the mercury is extruded through the perforation into Contact with the related metal ring III of the upper roller. During the time that the perforation is passing the line of centers of the rollers, an impulse is transmitted across the conductive path then formed between the lower roller and the ring of the upper roller, in a manner to be described presently. As the card moves past the line of centers and the pressure is relieved, the mercury withdraws from contact with the ring of the upper roller and from the perforation in the card, due to its inherent strong surface tension, and returns to its normal form, as shown at the right in Fig. 6.

' The sizeof the hole in the card in Fig. 6 is exaggerated, for clearer visibility. VIn practice it can be a mere puncture, such as can be made by a needle, or by a high tension electrical spark discharge. Under the conditions existing between the rollers, with the small pool of mercury conned and subjected to pressure, the smallest perforation in the card will release a thread of mercury into contact with the upper roller.

The smallness of the perforation can be taken advantage of in either, or both, of two ways. The area of the card allotted to one index point can be reduced, thus permitting a greater amount of data to be recorded on a given card area. On the other hand, a greater tolerance can be allowed for variations in position of the perforations, caused by atmospheric influences on the cards, for example. If the center of a hole in the card is shifted a sucient distance from the exact center of its index point position in the reading mechanism, it may cause an error by providing a conductive path in an adjacent index point position. The center of a hole of the small size contemplated herein would have to shift further from the exact center of its index point position, to make a conductive path in an adjacent index point position, than would the center of a larger hole. The embodiment shown in Fig. 6 has the additional advantage that the limits of tolerance are exactly dened by the area of the mercury pocket and are not subject to such variations as may occur where the area of contact of a flexible wire brush determines the boundaries within which an electrical impulse may be passed.

While the construction shown in Fig. 6 is preferred, other constructions will also perform the sensing function in accordance with the invention. Thus, in Fig. 7 the lower roller comprises a central metal shaft 42a, an insulating sleeve Iila, a metal sleeve iIa, and a relatively thin rubber cylinder IIlZu, having pockets I3a for the drops of mercury Iiia. In this case the amalgam plugs in the pockets are dispensed with, the mercury adhering directly to the metal cylinder IIa which is preferably composed of silver, or silver plated. The drops Iilc may be composed of a mercury amalgam, which is sufficiently stiff to retain a shape imparted to it, but suciently fluid to penetrate a perforation in the card and make contact with the upper roller, when subjected to pressure between the rollers.

In Fig. 3 the lower roller has a continuous coating of electrically conductive fluid, preferably mercury, or amalgam. The shaft 2b is again covered with a cylinder of insulation Iflilb, which is enclosed in a cylinder Ilb, the surface of which has an affinity for the electrically conductive fluid, which forms a continuous layer Ilb. If the layer Ib is mercury, or an amalgam, the sleeve lillb may be a metal such as silver or copper, having an afnity for mercury, or may be a metal lacking amnity with mercury, plated with a metal such as silver or copper, or otherwise treated on its surface to give it an aflinity for mercury, as by giving it a grainedor knurled character. On the other hand, the sleeve IQIb may be of rubber conditioned to give its surface an affinity for mercury. This can bedone in variousways, such as by roughening its Surface, coating it with rubber cement, or with a coating containing a powder of metal, such as silver or copper, having an ainity for mercury, or by incorporating a powder of such a metal into the body of the rubber layer |Ib. If the layer IOIb is non-conductive, radially, the insulating cylinder |000. can be omitted.

Operation of the machine With a stack of cards in the feed hopper 25 of the machine, and with the motor M started by closure of motor switch SW, the reading of the cards is ready to begin. The start switch ST is pressed, energizing magnet CFM through a circuit running from line wire |20, wire I2I, stop switch SP, start switch ST, wire |22, magnet CFM, and wire |23 to-line wire |24. The latch I8 rocks back, closing contacts |25 and thereby completing a holding circuit for magnet CFM, through stop switch SP. On release of the arm |4 and finger |1a by the latch I8, the dog I1 drops upon the notched disk I3 and, on entering the notch, sets the gear I6 in rotation. The card picker is reciprocated by the lever 21 and feeds the bottom card to feed rollers 30, 3|, which feed it to the second pair of feed rollers 32, 33, by which it is transmitted to the sensing rollers 34 and 35. In the course of the second cycle of the gear I6 the leading edge of the card passes under and raises a card lever |26, closing contacts |21. This occurs before the 9 index point position reaches the bite of the sensing rollers and while an emitter cam I 28 is holding its contacts I 23 open. The cam |28 is shown as mounted on shaft 88 (see dot and dash line 88a), so as to rotate in synchronism with the card feed. If a perforation appears in a 9 index point position (as in column l of the card shown in Fig. 9) the drop of mercury in the related pocket |03 will be pressed through the perforation, into contact with the opposite ring of the roller 35. During the time this contact is made the first tooth of cam |28 will close the switch |29, completing the following circuit: From line wire |20, through wire |30, contacts |29, wire |3I, contacts |21, wire |32, the metal trough |05, the mercury bath |06 (see Fig. 4), through the amalgam plugs |04 at the bottom of roller 34 which are submerged in the mercury bath, through the metal cylinder |0| (see Fig. 6), the top plug |04, via the drop of mercury |08 through the hole in the card, through the ring |I and itsbrush I I3, terminal ||5, wire I 33, magnet 96, pertaining to column 1, and wire |34 to line wire |24, energizing said magnet 96. The dog 90 drops in front of the first tooth 91 of the column l type bar, setting the 9 type member thereof in printing position. When the 8 index point row of the record card passes between the sensing rollers 34 and 35, in any column where. a hole appears (as in column 2 of the card shown in Fig. 9) the mercury in the related pocket of the roller 34 will be pressed through the hole into contact with the appertaining ring |I| of the roller 35. During the period of this contact the second tooth of cam I 28 will close contacts |28 and an impulse will be transmitted through a circuit similar to the one previously traced, through magnet S0 pertaining to column 2. The related dog 90 will engage the second tooth of the type bar for column 2 and the 8 type member will be set in printingv position. When the last index point row of the cardv has passed the sensing rollers and the type bars have been set in accordance with the data on the card, the hammers l2 are actuated in the-customaryman ner, as shown, for example, inthe above men- 8 tioned Lake Patent 1,822,594, to make the printed recordof the data..

When no card is between the sensing rollers contact is made between each pocket of mercury and the upperroller, but at this time the card lever contacts |21 are open, consequently the ymagnets 96 are not energized. During the time that the card lever contacts are closed the cam operated contacts |29 are only closed intermittently, within the portion of the machine cycle in which the twelve index point positions pass between the sensing rollers. Therefore the magnets can only be energized when contact is made by the mercury through a hole in the card.

If the lower sensing roller has the structure shown in Fig. 8, the circuit from the mercury bath |06 to the upper roller 35 is through the continuous layer of mercury on the surface of the lower roller, and through the sleeve |0|b, if the latter is composed of conductive material.

A further illustration of the invention appears in Figs. 10, 11 and 12, which show a record sensing mechanism similar to the one rst described, but with the card lever replaced by an electrical contact comprising an electrically conductive fluid as the effective sensing instrumentality, in accordance with the principle of the invention. The lower sensing roller 340 comprises a central shaft 420 surrounded by an insulating sleeve |603, which is covered by a cylinder |0|c, of silver or other suitable electrically conductive material. A rubber sleeve |020 surrounds the cylinder |0|c and is similar to the sleeve |02 in Fig. 6, except in the end zone, where the card lever |26 is located in Fig. 3. As shown in the enlarged cross section, Fig. 11, the rubber sleeve |020 has perforations |030 which are lled with a solid, or semi-solid conductive substance |040, such as the mercury amalgam previously referred to. In this case, the amalgam is continuous from one perforation |030 to the next, to provide a continuous layer thereof in the bottom of the annular groove |50 in the sleeve |020. This groove contains a continuous ring |5| of a iiuid conductor, such as mercury, or a iiuid amalgam, which is replenished from the bath |060 in the bottom of trough |050, within which the roller revolves. The upper roller 350 has an additional ring |I|c positioned for coaction with the ring of mercury |5I.

As shown in Fig. l0, the circuits to the print magnets, represented by magnet S0, extend from line wire |20 through wire I 52 to the trough |050, thence through the fluid |000 and the roller 340, as previously traced, to a disk of the upper roller, brush I3, wire |33, coils of magnet S0, bus bar |53, contacts |29 and |210 to the other line wire |24. The contacts |210 are controlled by a relay magnet |56 which is in a circuit controlled by the record card C, in the manner of a card lever control. This circuit extends from the trough |050 and fluid conductor |050, through the ring of mercury |5| to disk Ic coacting therewith, thence through a brush H30, wire |51, the coil of relay magnet |50, and wire |58 containing a resistance |59 to line wire |24. The relay |56 is thus energized when no card is between the rollers 340 and 350 and at such times holds the contacts |210 open, disabling the print magnets 9-3. When the leading edge of the card C -moves between the two rollers, it breaks the circuit of the relay |56, deenergizing the relay and allowing contacts I 21o close. The circuits of the print magnets are and pointed out the fundamental novel features of the invention as exemplified in certain embodiments of the invention, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated and in their operationmay be made by those skilled in the art, without departing from the spirit' of the invention. It is the intention, therefore, to be limited onlyvas indicated by the scope of the following claims.

What is claimed is:

1. In a device for sensing perforated records, two parallel rollers mounted close together so as to be capable of compressing records fed between them, one of said rollers having at its surface an electrically conductive liquid, the liquid and surface of the roller having a mutual aiiinity which causes the liquid to adhere to said surface, and the liquid being adapted to be extruded through any perforation in the record into contact with the other roller, when the portion of the record containing such perforation is compressed between said rollers, the other roller having an electrically conductive surface for engagement by said extruded liquid, and means for connecting said electrically conductive liquid and the electricaly conductive surface of said other roller to a source of electric current.

2. In a device for sensing perforated records, a pair of parallel rollers. a trough in which one of said rollers is revolubly mounted, a bath of electrically conductive liquid in said trough making contact with said latter roller, the liquid and the surface of the latter roller having a mutual affinity which causes the liquid to adhere to said surface, means to rotate said rollers, said rollers being mounted in such proximity to each other as to be capable of feeding a perforated record therebetween with pressure, whereby electrically conductive liquid picked up from said trough by the roller revolving therein will be extruded through any perforations in the record into contact with the other roller, the other roller having an electrically conductive surface for engagement by said extruded liquid, and means for connecting said electrically conductive liquid and the electrically conductive surface of said other roller to a source of electric current.

3. In a device for sensing perforated records, a pair of parallel rollers. a trough in which one of said rollers is revolubly mounted. said latter roller having on its surface an elastic layer with perforations containing solid metal plugs. means to rotate said rollers, a bath of an electrically conductive liquid in said trough. the liquid and said metal nlugs having a mutual affinity which causes the liquid to adhere to said metal plugs as the roller in said trough revolves, said rollers being mounted in such proximity to each other as to be capable of feeding a perforated record therebetween with pressure, whereby electrically conductive liquid on said plugs will be extruded through any nerforations in portions of the record overlying said plugs, into contact with the other roller, the other roller having an electrically conductive surface for engagement 'by said extruded liquid` and means for connecting said solid metal plugsy and the electrically conductive surface of said other roller to a source of electric current.

4. Electrical contact means for detecting perforations in an insulating layer, comprising a solid member adapted to be positioned against one side of the insulating layer and having electrical contact means electrically connected to one terminal of a source of electricity. a second member comprising an elastic cup substantially filled with an electrically conductive liquid and provided with electricaiy conductive means to lead off current from said electrically conductive liquid to the other terminal of said source of current, said second member being movable to press said'cup and the electrically conductive liquid therein against the opposite side of the insulating layer from said solid member. the elastic cup being adapted to seal in the liquid so that a pressure is exerted to extrude the liquid through any perforation in the insulating layer within the area bounded by the cup into contact with the electrical contact means of said solid member.

5. In ardevice for sensing perforated records, two record engaging members one of which comprises elastic material, said members being mounted so as to be capable of relative movement to compress between them a perforated record to be sensed, one of said members having at its surface an electrically conductive liquid adapted to be extruded through any perforation in the record into contact with the other member, when the record material surrounding such perforation is compressed between -said members, whereby the electrically conductive liquid is forcibly extruded through the perforations. said other member having an electrically conductive surface for engagement by said extruded liquid, and means for connecting said conductive liquid and the electrically conductive surface of said other member to a source of electric current.

6. In a device for sensing perforated records, two record engaging members mounted so as to be capable of relative movement to compress between them a perforated record to be sensed, one of said members having a surface of elastic material coated with an electrically conductive liquid adapted to be extruded through any perforation in the record into contact with the other member, when the record material surrounding such perforation is compressed betweensaid members, whereby the electrically conductive liquid is forcibly extruded through the perforations, said other member having an electrically conductive surface for engagement by said eX- truded liquid. and means for connecting said conductive liquid and the electrically conductive surface of said other member to a source of electric current.

'7. In a device for sensing perforated records, two record engaging members mounted so as to be capable of relative movement to compress between them a perforated record to be sensed, one of said members comprising elastic material with depressions containing an electrically conductive liquid adapted to be extruded through 2,43 IJIE' liquid, and means for connectingzsaid conductive liquid andthe electrically conductive surface ofv saidother member to a source of electric current.-

8. In a-device for sensing perforated records, two record engaging members-mounted so as to becapable of relative movement to compress between them a perforated record. to be sensed, one ofsaid members comprising elastic material with depressions containing a-solid electrically conductive material and an electrically conductive liquid mutually cohesive with said solid electrically conductive material on vthe sul"- face of the latter, said liquid being'adapted to be extrudedthrough anyperforation in the recordinto contact with the other member, when the. 15

facevr for engagement byfsaid-extruded liquid.'

5 member lto 'a source o! electric current.

ROBERT E; PARIS.

REFERENCES' CITED The following references are o! record in the 1 me of this patent:

UNITED STATES PATENTS Number:v Name-U Date 1,041,294 Kelly ---i oct. 15, 1912 2,207,406 Jonesiz.` July 9, 1940 .2,147,506 Stoner. Feb. 14, 1939 1,106,907 Wilkinson Aug. 11, 1914 677,214 Hollerith June 25, 1901 1,572,212'-v Lonz -'Feb. 9, 1926 1,827,362 Hiltz et ai; Oct. 13, 1931 

